The present invention relates to a central vacuum cleaning unit, and more particularly to a central vacuum cleaning unit including an energy recovery ventilator system
Modern residential and commercial buildings, especially single family homes, are built to resist external weather conditions. Construction techniques and materials are chosen to seal buildings so that air exchange between the interior and the exterior of the building is minimized to reduce heating and cooling costs. As a convenience, many buildings are also provided with a central vacuum system used to clean floors and other surfaces in the building. Briefly, a central vacuum system includes a motor driven vacuum unit, vacuum ports located throughout the structure, duct work placed in the walls of the building to connect the vacuum unit to the vacuum ports and a user manipulable cleaning attachment which mates with the vacuum ports. The vacuum source is typically placed in a somewhat remote location, such as a garage. Electrical cabling can be installed with the duct work to provide an electrical connection between the vacuum unit and the cleaning attachment. Such an electrical connection is used to switch the vacuum unit on or off. Other electrical connections can be used to power a rotary brush mounted on the cleaning attachment.
As the central vacuum system operates, air is exhausted from the building. This depletes the air inside the building, especially in buildings that are well sealed to prevent air transfer between the interior and exterior of the building. Various ways to introduce air into buildings are known in the art of building ventilation. As an example, U.S. Pat. No. 2,725,113, incorporated herein by reference, discloses a central vacuum system where both a fresh air supply opening and a vacuum source opening are provided on panels throughout the building. When the central vacuum is operating, a common motor supplies fresh air and suction to the panel being used by an operator. However, this example system does not balance the air flow of exhausted air and fresh air.
Air exchangers, otherwise referred to as air to air heat exchangers or heat recovery ventilators, for providing a balanced flow of air into and out of a building are also known. For example, U.S. Pat. No. 5,257,736, incorporated herein by reference, discloses an air exchanger having a pressure sensor. If the sensor detects a negative pressure in the building, the air exchanger stops pumping air out of the building to balance the air pressure. Air exchangers typically provide a range of functions such as reducing air contamination, heating or cooling air entering the building, and/or humidifying or dehumidifying air entering the building. Accordingly, the air exchanger is usually connected to the rest of the building's ventilation system and operates independently of other appliances. Operation of the vacuum is determined by sensing the resulting pressure differentiation rather than by an electrical connection.
U.S. Pat. No. 6,218,798 B1 to Price et al., incorporated herein by reference, is discloses an interface for linking a central vacuum unit with an air exchanger. A motor is provided to the central vacuum to create sufficient negative pressure for vacuuming a household surface. Similarly, a motor is provided to the air exchanger to supply air to an interior environment from an exterior environment while the central vacuum is being operated. Outside air drawn in through a fresh air inlet of the air exchanger is supplied to an interior environment when the vacuum is activated. Fresh air being vented to the interior environment and the stale air being exhausted externally is filtered through filter cartridges to remove debris from the air streams. The interface links the central vacuum unit with the air exchanger to provide synchronized, cooperative operation.
However, the central vacuum disclosed in U.S. Pat. No. 6,218,798 B1 does not operate in cooperation with the air exchanger when vacuuming is not required. Such operation would be noisy and energy inefficient since central vacuum units typically operate at a high air flow rate in order to produce a sufficient vacuum. Further, the system of U.S. Pat. No. 6,218,798 B1 is costly since the central vacuum unit, the air exchanger and the interface must each be purchased separately.